The Large Hadron Collider: The Big Bang Machine

Transcription

1 The Large Hadron Collider: The Big Bang Machine Albert De Roeck CERN, Geneva, Switzerland Antwerp University Belgium Davis University USA IPPP, Durham UK 3 May 2012

2 Contents In this talk I will present and discuss the most complex, most challenging and at the same time one of the most anticipated scientific instruments so far built by mankind: The Large Hadron Collider (LHC), built at CERN, Switzerland What are the fundamental questions in particle physics? What is the Large Hadron Collider? What is the science of the Large Hadron Collider?

3 CERN: The European Laboratory for Particle Physics CERN is the European Organization for Nuclear Research, the world s largest Particle Physics Centre, near Geneva, Switzerland It is now commonly referred to as European Laboratory for Particle Physics It was founded in 1954 and has 20 member states + several observer states CERN employes >3000 people + hosts ~10000 visitors from >500 universities. Annual budget ~ 1100 MCHF/year (2011)

4 Breaking the Walls between Cultures and Nations since 1954

5 Breaking the Wall of Communication 20 years ago: the Web was born Brazil and CERN / September

6 CERN Provides Particle Beams & Research Infrastructure Why do we need particle accelerators?

7 What is the world made of? What holds the world together? Where did we come from? Particle physics is a modern name for centuries old effort to understand the laws of Nature E. Witten (String Theorist)

8 Accelerators are Powerful Microscopes They make high energy particle beams that allow us to see small things. wavelength λ = h p Planck constant momentum ~ Energy seen by low energy beam of particles (poorer resolution) seen by high energy beam of particles (better resolution)

9 We can create particles from energy Two beams of protons collide and generate, in a very tiny space, temperatures over a billion times higher than those prevailing at the center of the Sun.

10 Illustrating the experiment E=mc2 Highly Expected Hypothetical Unsuspected? extinct since Big Bang SUSY

11 Matter and Forces Matter Forces To remove a proton from a nucleus need ~10 MeV ~10 million To remove an electron from an atom need ~10 ev 10 All forces in the world can be attributed to these four interactions

12 The Standard Model Over the last 100 years: combination of Quantum Mechanics and Special Theory of relativity along with all new particles discovered has led to the Standard Model of Particle Physics. The new (final?) Periodic Table of fundamental elements Matter particles Force particles A crowning achievement of 20th Century Science The SM has been tested thousands of times, to excellent precision. Yet, its most basic mechanism, that of granting mass to particles, the Higgs boson (?), is still missing! And where is GRAVITY?

13 Particle Masses Mass proportional to area: νe νµ ντ e µ τ u d s c b... top quark photon gluons W Z Higgs? A large variety of masses in Nature! Why?...

14 The Origin of Particle Masses A most basic question is why particles have masses and so different masses Peter Higgs The mass mystery could be solved with the Higgs mechanism which predicts the existence of a new elementary particle, the Higgs particle (theory 1964, P. Higgs, R. Brout and F. Englert) The Higgs (H) particle has been searched for since decades at accelerators, but not yet found The LHC will have sufficient energy to produce it for sure, if it exists Francois Englert 14

15 Dark Matter in the Universe Astronomers found that most of the matter in the Universe must be invisible Dark Matter Vera Rubin ~ 1970 Supersymmetric particles? F. Zwicky

16 Accelerators Create (anti)particles that existed ~0.001 nanosecond after Big Bang LHC E = mc2 Inflation Big Bang One Force Four Forces particles anti-particles Do all the forces become one?

17 This Study Requires. 1. Accelerators : powerful machines that accelerate particles to extremely high energies and bring them into collision with other particles 2. Detectors : gigantic instruments that record the resulting particles as they stream out from the point of collision. 3. Computing : to collect, store, distribute and analyse the vast amount of data produced by these detectors 4. Collaborative Science on Worldwide scale : thousands of scientists, engineers, technicians and support staff to design, build and operate these complex machines.

18 A New Era in Fundamental Science was Launched in March 2010 Start-up of the Large Hadron Collider (LHC), one of the largest and truly global scientific projects ever, is the most exciting turning point in particle physics. CMS Exploration of a new energy frontier Proton-proton collisions at ECM = 14 TeV LHC ring: 27 km circumference ATLAS ALICE Drexel'11tsv 18

19 The Large Hadron Collider LHC

20 The Large Hadron Collider = a proton proton collider 7 TeV + 7 TeV (3.5 TeV TeV) 1 TeV = 1 Tera electron volt = 1012 electron volt Primary physics targets Origin of mass Nature of Dark Matter Understanding space time Matter versus antimatter Primordial plasma The LHC is a Discovery Machine The LHC will determine the Future course of High Energy Physics

21 Several thousand billion protons Each with the energy of a fly % of light speed They orbit a 27km ring times/second A billion collisions a second in the experiments

22 LHC facts The emptiest space in the solar system To accelerate protons to almost the speed of light, we need a vacuum similar to interplanetary space. The pressure in the beampipes of the LHC will be about ten times lower than on the moon.

23 LHC facts One of the coldest places in the Universe Methodology the largest cryogenic system ever built 54 km fridge! With a temperature of around -271 degrees Celsius, or 1.9 degrees above absolute zero, the LHC is colder than interstellar space.

24 LHC facts One of the hottest places in the Galaxy Simulation of a collision in the CMS experiment Simulation of a collision in the ALICE experiment When two beams of protons collide, they generate within a tiny volume, temperatures more than a billion times those in the very heart of the Sun.

25 Experiments at the LHC

26 The Four Central Experiments ATLAS CMS ALICE LHCb Thai groups interested in CMS and ALICE: data analysis, computing, upgrade..

27 Schematic of a LHC Detector Physics requirements drive the design! Analogy with a cylindrical onion: Technologically advanced detectors comprising many layers, each designed to perform a specific task. Together these layers allow us to identify and precisely measure the energies and directions of all the particles produced in collisions. Such an experiment has ~ 100 Million read-out channels!! Drexel'11tsv

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29 The CMS Collaboration: 3400 scientists and engineers, ~840 students from 173 Institutions in 41 countries. ~ 1/6 of the people who made CMS possible CMS = Compact Muon Solenoid

30 Installing the Experiment Jul

31 Cables, Pipes and Optical Fibres! Nov 2007 Took man hours Drexel'11tsv 31

32 CMS before closure

33 CMS Detector ready for operation Drexel'11tsv

34 The CMS experiment (IP5) The Compact Muon Solenoid

35 The LHC Data Challenge The LHC accelerator will run for years Experiments will produce about 15 Million Gigabytes of data each year (about 20 million CDs!) LHC data analysis requires a computing power equivalent to ~100,000 of today's fastest PC processors Requires many cooperating computer centres, as CERN can only provide ~20% of the capacity GRID Computing

36 The Grid at Work Worldwide LHC Computing Grid connects 100,000 processors in 34 countries with ultra-high-speed data transfers Millions of Gigabytes of data each year.

37 The Physics Program at LHC I will give a few examples(*) but we have now more than 100 results from LHC -Are quarks the elementary particles? -Do we see supersymmetric particles? -Do we see extra space dimensions? -Do we see micro-black holes? -Do we see the Higgs Boson? (*) Many papers on measurements of the electroweak and strong force not discussed here

38 March : Collisions at 7 TeV 38

39 Are Quarks Elementary Particles? Measurement of the production angle of the jet with respect to the beam -> High Energy Rutherford Experiment Quarks remain elementary particles after these first results

40 Beyond the Higgs Boson Supersymmetry: a new symmetry in Nature? Candidate particles for Dark Matter Produce Dark Matter in the lab SUSY particle production at the LHC Picture from Marusa Bradac

41 Detecting Supersymmetric Particles Energy produced in the detector Supersymmetric particles decay and produce a cascade of jets, leptons and missing (transverse) energy due to escaping dark matter particles Very clear signatures in CMS and ATLAS LHC can discover supersymmetric partners of the quarks and gluons as heavy as 2 to 3 TeV The expected cross sections are huge!! 10,000 to 100,000 particles per year

42 Do we see Supersymmetric Particles? So far NO clear signal of supersymmetric particles has been found We can exclude regions where the new particles could exist. Searches will continue for the next years m0 and m1/2 are SUSY parameters Masses of SUSY particles are larger than 1000 GeV!!! So these particles are heavier than 1000 times the proton Explore other than the simplest/constrained SUSY models

43 Some Interesting Collisions Events with five jets of particles and large missing energy which could come from a possible dark matter particle But a few events is not enough too prove we have something new

44 Extra Space Dimensions Problem: The Gravity force becomes strong!

45 Extra Dimensions at the LHC Main detection modes at the experiments Collisions with Large missing (transverse) energy Resonance production in two particle distributions No signal yet If extra dimensions exist then the Planck scale is larger than 2-3 TeV LHC can detect extra dimensions for scales up to 5 to 9 TeV

46 Quantum Black Holes at the LHC? Black Holes are a direct prediction of Einstein s general theory on relativity If the Planck scale is in ~TeV region: can expect Quantum Black Hole production Quantum Black Holes are harmless for the environment: they will decay within less than seconds SAFE! Simulation of a Quantum Black Hole event Quantum Black Holes open the exciting perspective to study Quantum Gravity in the lab!

47 Search for Micro-black Holes Extra Dimensions! RS Planck scale a few TeV? Evaporates in sec No evidence for micro black holes was found in the data so far But some do see some interesting events These could be background Black holes with mass of up to 5 TeV are excluded (model dependent)

48 Black Holes Hunters at the LHC

49 A funny thing happened Before Christmas Press from ~ 15 December What is all this fuzz about?

50 The Hunt for the Higgs Where do the masses come from? The key question: Where is the Higgs? We do not know the mass of the Higgs Boson Scalar field with at least one scalar particle It could be anywhere from 114 to 700 GeV 50

51 The Higgs Boson Peter Higgs

52 Understanding the Higgs Search Plots For a Higgs signal we need an excess above the red line

53 Higgs Boson Searches Low MH < 140 GeV/c2 Medium 130<MH<500 GeV/c2 High MH > ~500 GeV/c2

54 Where is the Standard Model Higgs Boson? Summary of the results shown at the Summer 2011 conferences Still allowed For a Higgs signal we need an excess above the red line excluded A propos: If we would exclude the Higgs in the full mass range, this would be a major discovery!!! Then new phenomena are expected to be observed ~1 LHC

55 Searches for the Higgs Particle A Higgs particle will decay immediately, eg in two heavy quarks or two heavy (W,Z) bosons Example: Higgs(?) decays into ZZ and each Z boson decays into μμ So we look for 4 muons in the detector But two Z bosons can also be produced in LHC collisions, without involving a Higgs! We cannot say for on event by event (we can use the total invariant mass of the 4 muons)

56 A Collision with two Photons A Higgs or a background process without a Higgs?

57 Results from the Experiments Higgs 2 photons?? Higgs 2 Z 4 leptons?? Some excess of events seen in both experiments within a mass range of 5-6 GeV. Low statistics still. Is this significant? Not by eye! But sophisticated Statistical Methods have been used to fully analyse this. And the result is

58 The Results of the Higgs Search 2011 For a Higgs signal we need an excess above the red line Results 1) The mass region where Higgs particle can possibly live has been reduced to very small mass range of GeV (95% CL) 2) We see an excess of events in that region over expectation from pure background. Cool! Is this the first sign of the growing Higgs signal? Is it a statistical fluctuation in the background? We can t say for sure. These questions will be answered with the 2012 data (4 x 2011 data)

59 So, where is the Higgs Boson? The experiments analysed the new data, for the full year of 2011 They can exclude an even larger range, and restrict the region for the Higgs to GeV But.. they see a tantalizing excess in the Higgs mass range of GeV. This is exciting! The significance of this excess is still far too low to claim a discovery, but a Higgs signal could just start to be seen just like that. The excess could still go away with more data. The LHC 2012 data will be the referee But of course we have our hopes! The Higgs boson could well be showing signs of life already

60 Matter-Antimatter The properties and subtle differences of matter and antimatter using mesons containing the beauty quark, will be studied further in the LHCb experiment

61 Angels and Demons? Does the LHC produce antiprotons? Yes: these are produced in the pp collisions but at a very low rate: we would have by now about antiprotons, if we could collect all of them Fermilab (Chicago) has a proton anti-proton collider. The have a factory to make antiprotons. They produced about 4 x 1015 antiprotons in the last 20 years. This is micrograms only. This is much much less than in Dan Brown s book

62 Primordial Plasma Lead atom on lead atom collisions at the LHC to study the primordial plasma, a state of matter in the early moments of the Universe More than 10,000 particles per event in the detector Study the phase transition of a state of quark gluon plasma created at the time of the early Universe to the baryonic matter we observe today A lead lead collision simulated in the ALICE detector

63 A Recorded Heavy Ion Collision

64 Important Visits to CERN

65 Thailand and the LHC 2008: Delegation of CERN/CMS visits Thailand 2009: CMS and Thailand (SLRI) sign an expression of interest 2010: CERN-Thailand Joint School on particle physics in Bangkok 2010: First PhD of a student from Thailand on the LHC : Setting up of a Tier2 for Computing in Thailand 2012: Expect Chulalongkorn University to officially join the CMS experiment: possibilities for PhDs and Master theses in CMS 2012: Expect SUT to become an associate member of ALICE 2012: 2nd CERN- Thailand joint school in SUT (April-May) Contributions to Computing (Tier2) for data production and analysis Calibration of the detectors. Our daily work! Upgrades of CMS Data analysis in searches for new physics, and others Excellent opportunities for young students to join the LHC adventure

66 CERN is also: Technology Transfer GRID Computing! Silicon detector for a Compton camera in nuclear medical imaging Radio-isotope production for medical applications Thin films by sputtering or evaporation Medipix: Medical X-ray diagnosis with contrast enhancement and dose reduction Radiography of a bat, recorded with a GEM detector

67 6 7 Bringing the Nations Together the promotion of contacts between, and the interchange of, scientists

68 Electro-weak phase transition (ATLAS, CMS ) QCD phase transition (ALICE ) LHC will study the first seconds 68

69 The LHC will reveal the origin of mass of particles It will very likely reveal much more. There is mounting evidence, from neutrino mass to dark matter and dark energy observations, that there is something profound that we do not yet understand Is it supersymmetry, extra dimensions, other? The LHC operates at an energy and precision that takes us far beyond our current understanding, into a new regime The LHC experiments are taking data since 2010 in this new regime. First physics results do not yet show signatures for new physics but these can come now any day! Watch the Higgs in 2012! We are on the verge of a revolution in our understanding of the Universe and our place within it. Thai scientists can take part in this science revolution

70 Note: LHC is not the only project at CERN Question since a few weeks: Are neutrinos superluminal? OPERA experiment suggests that High energy neutrinos move faster than the speed of light (by %). Enormously far reaching implications! 732 km Neutrinos arrive 6010 nanoseconds faster than expected Jury is still out: Next steps -Further checks made following suggestions after release -Use different beam structure, allowing to check the timing? -An independent check by another experiment (MINOS/US, T2K/Japan?) Theory finds it difficult to accommodate this consistently

71 CERN as an Educator Apprentices Academic Training Accelerator School Fellows Exhibitions CERN-Latin America School Visits Doctoral Students Physics School Computing School Technical Students Outreach Technical Training Summer Students Microcosm Science on Stage Teachers programmes Conferences Language Training Communications Training Management Training 71

72 Candidate Multi Jet Event at 2.36 TeV 72

73 Are there undiscovered principles of nature: New symmetries, new physical laws? 2. How can we solve the mystery of dark energy? 3. Are there extra dimensions of space? 4. Do all the forces become one? 5. Why are there so many kinds of particles? 6. What is dark matter? How can we make it in the laboratory? 7. What are neutrinos telling us? 8. How did the universe come to be? 9. What happened to the antimatter? 10. What is mass? Evolved Thinker Quantum Universe and Discovering the Quantum Universe Discoveries and breakthroughs will likely come from Energy Frontier Accelerators at the Terascale.

74 The LHC Detectors are Major Challenges CMS/ATLAS detectors have about 100 million read-out channels Collisions in the detectors happen every 25 nanoseconds ATLAS uses over 3000 km of cables in the experiment The data volume recorded at the front-end in CMS is 1 TB/second which is equivalent to the world wide communication network traffic Data recorded during the years of LHC life will be about all the words spoken by mankind since its appearance on earth A worry for the detectors: the kinetic energy of the beam is that of a small aircraft carrier of 104 tons going 20 miles/ hour >200 m2 of silicon ATLAS pixel detector CMS silicon tracker

75 Applications of Grid Computing Multitude of applications from a growing number of domains Archeology Astronomy & Astrophysics Civil Protection Computational Chemistry Earth Sciences Financial Simulation Fusion Geophysics High Energy Physics Life Sciences Multimedia Material Sciences Infrastructure used by >5000 researchers - submitted ~20 millions jobs in 2006

76 Results from the Experiments Higgs 2 photons?? Higgs 2 Z 4 leptons?? Some excess of events seen in both experiments within a mass range of 5-6 GeV. Low statistics. Is this significant? Not by eye! But sophisticated Statistical Methods have used to fully analyse this. And the result is